Attenuators are designed to introduce a known loss between two or more nodes in a circuit. Often, these devices are utilized in radio frequency (RF) circuits, audio equipment, and measuring instruments to lower voltage, dissipate power, and/or for impedance matching. Attenuators may be passive attenuators, variable attenuators, and/or temperature compensation attenuators. Passive attenuators are designed with passive components, such as resistors, to introduce a designed loss between the nodes of a circuit. Passive attenuators generally have fixed impedance levels. Unfortunately, passive attenuators are not dynamic and modifying their impedance levels requires physically changing the passive components in the passive attenuator.
Variable attenuators are capable of varying their impedance levels. For example, a digitally controlled attenuator (DCA), also known as a step attenuator, may include a stack of transistors coupled to passive components. These transistors act as switches and vary the impedance level by being turned on and off so as to introduce the attenuation of the passive components selected by the transistors. However, since the impedance level of the digitally controlled attenuator can only vary in accordance with the attenuation being introduced by the passive components coupled to the transistors, the impedance levels of the DCA are discrete and thus the attenuation range of the DCA suffers from low resolution.
Other variable attenuators, such as voltage controlled attenuators (VCA), include active components that allow the VCA's impedance level to vary within a continuous impedance range. These active components may, for example, be individual transistors placed in different circuit segments of the VCA. Unfortunately, these types of VCA's suffer from a high degree of distortion. To ameliorate the distortion in the VCA, prior art VCA's use pin diodes and quadrature hybrid techniques. These techniques however provide VCAs with very limited bandwidth. Also, these solutions are relatively expensive.
Thus, there remains a need for a variable attenuator with a high dynamic attenuation range and/or a wide bandwidth and low distortion that is relatively inexpensive.
Temperature compensation attenuators are designed to compensate for variations in attenuation caused by changes in temperature of the attenuation components of the attenuator. Generally, temperature compensation attenuators modify the operation of the attenuation components to compensate for changes in attenuation that result from changes in temperature. Unfortunately, many temperature compensation attenuators also have very limited bandwidth and/or do not have low distortion or a control voltage that is easily adjustable to compensate for temperature changes in the attenuator.
Accordingly, there remains a need for a temperature compensation attenuator with a dynamic attenuation range and/or a wide bandwidth and low distortion that is relatively inexpensive.
Temperature controlled attenuators are designed to create a temperature dependant attenuation that compensate for variations in gain of a cascade of amplifiers, mixers and other electronic components caused by changes in temperature of the components. Generally, temperature controlled attenuators modify the operation of the attenuation components to compensate for changes in gain of the other components in the lineup that result from changes in temperature. Unfortunately, many temperature controlled attenuators also have very limited bandwidth and/or do not have low distortion or an easily adjustable/programmable temperature coefficient.
Accordingly, there remains a need for a temperature compensation attenuator with a dynamic attenuation range and/or a wide bandwidth and low distortion that is relatively inexpensive.